Regulation of the Cell Cycle Is Dependent on Cyclins and Cyclin-Dependent

Multiple Choice

Regulation of the cell cycle is dependent on cyclins and cyclin-dependent kinases (CDKs) .The key factor that allows a cell to progress beyond the restriction point in G1 is

A) the presence of cyclin.
B) the absence of cyclin.
C) the presence of cyclin and CDK.
D) phosphorylation of RB by CDK.
E) the presence of external signals from growth factors.